2020 Ram 1500 Limited P1A20 - Hybrid Battery System Precharge Time Too Long

[Lashlarue]

The truck battery discharged enough from 3 weeks of not running that it put up a low voltage warning (11.9v). It started but would not allow the alternator to charge. After charging, clearing codes, and restarting (rinse, repeat 3 times), I'm still getting a P1A20 error and the alternator won't run. O'Reiley tested the battery and it passed. I used a multimeter and the battery looks good. It is one year old.

I ran the engine for 15 or 20 minutes while watching the voltmeter slowly drop from 12.4 to 12.1. After charging it's over 13 even after an hours rest off the charger.

Grok suggested it could be the battery sensor on the negative terminal. O'Reiley doesn't sell them (yet). I'll make a run to the local dealer and pick it up in the morning.

Has anyone fought their way through this? When my first battery died all I had to do is add a new one (enhanced flooded Super Start). Now I know I'm in trouble as no one sells this aftermarket and I've not found a match online for the ODBC code P1A20.

You know I'm sweating bullets it could be the hybrid system. Mucho Dinero. One mistake I have made was running a wire brush terminal cleaner through the negative terminal. That terminal includes a band that the sensor uses to read the voltage.

2020 Ram Limited 5.7l HEMI w econ 44K miles.

 

[Lashlarue]

Update: I charged the battery overnight and tested again today. It drops to 12.4v on the display, not enough to get the alternator to turn on. I measured w the multimeter and the truck's sensor is accurate. I'm charging again and will watch the voltage drop off with no load to see if it might be the battery. OReiley tested the battery and said it was good but I'm thinking not. Too bad I'll have to spend $300 for an AGM to find out if my almost new battery is the problem.

 

[Wild one]

Update: I charged the battery overnight and tested again today. It drops to 12.4v on the display, not enough to get the alternator to turn on. I measured w the multimeter and the truck's sensor is accurate. I'm charging again and will watch the voltage drop off with no load to see if it might be the battery. OReiley tested the battery and said it was good but I'm thinking not. Too bad I'll have to spend $300 for an AGM to find out if my almost new battery is the problem.

Spend 20 bucks and buy yourself one of these old school toaster style testers,and test the battery yourself before you buy a new battery.These are still one of the best battery testers a home mechanic can have in their tool box,far better then a newer digital tester,which is probably what OReiley uses.

100 Amp, 6/12V Battery Load Tester

Amazing deals on this 100 Amp 6/12V Battery Load Tester at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

 

[RamDiver]

^^^^
DITTO!

The digital load testers are prone to false positives because they don't actually apply a load like the toaster-style load tester.

.

 

[Lashlarue]

The truck is now at the dealer. The P1A20 code and needing to press start twice means the hybrid system is a problem. They will take days to look at it. I will post up what they find. The truck is supposed to be covered under an extended warranty for the hybrid battery and its charger.

 

[Lashlarue]

It's been all week and no call from the dealer. Just a promise they will look at it.

 

[Lashlarue]

OK time for closure. It was the hybrid battery pack and even tho the truck is 6 years old, they covered it under a special warranty that just covers the hybrid system. It took 17 days from drop off to pick up the working truck.

Turns out the alternator first checks the hybrid battery and will not spin the alternator if it's not happy with the hybrid power pack response. The same unit charge the starter motor battery.

I'm happy it's working and I was not out any $$$$.

Thanks for all the help.

 

[Lashlarue]

Update: two weeks and about 50 miles later the truck's main battery was dead. I was packing it for a week long trip I guess it was lucky it happened before I left. After a recharge of the starter battery I tested it at OReilly and AutoZone. Pushing the starter does nothing again. So I tried replacing the starter relays. Nothing. So it's been sitting the week I was gone and now another week while I wait for the road ice to clear. It's not even going to let me drive it to the dealer, its tow time.